Feasibility Study of a Medium Voltage 12 kV, 1 kA, LC DC Circuit Breaker

The paper studies design options for a 12 kV, 1 kA LC DC Circuit Breaker with multiple possible applications in future MV DC systems. The stresses on all main components are analysed under conservative assumptions, and evaluation of their implementation is provided. The ultrafast disconnector is the key component that is assumed to have 6 break points with 2.5 m/s rod velocity and 2 ms opening time. The peak current stress is obtained on detailed PSCAD simulation model as Icp=4.7 kA, with conservative assumptions for protection system. The parallel capacitor is the largest component, with the calculated main parameters VCs=18 kV, Cs=250 µF, and estimated weight of m=80 kg. The total energy dissipation is 220 kJ, that can be accommodated with 2 standard 5 kV railway arresters (210 kJ), while Cs takes another 10 kJ. The low-voltage pre-charged film capacitor Cch =6mF, 0.8 kV is of modest weight. It is concluded that the design is feasible with expected competitive performance and cost, relative to the commercial HV DC breakers.